Synthesis of acidic silica to upgrade heavy feeds

ABSTRACT

A method and a product made by treating a sulfur-containing hydrocarbon heavy feed, e.g., heavy crude asphaltene reduction is disposed herein. The method comprises the steps of: mixing the sulfur-containing hydrocarbon heavy feed with a hydrogen donor solvent and an addled silica to form a mixture and oxidizing the sulfur in the mixture at a temperature between 50° C. and 210° C. wherein the oxidation lowers the amount sulfur in the sulfur-containing hydrocarbon heavy feed by at least 90%.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/910,195, filed Jun. 5, 2014, entitled “SYNTHESIS OF ACIDIC SILICA TOUPGRADE HEAVY FEEDS;” which claims priority to U.S. ProvisionalApplication Ser. Nos. 61/186,178 and 61/286,238 filed Jun. 11, 2009 andNov. 30, 2009, respectively, and U.S. patent application Ser. No.12/814,012 filed Jun. 11, 2010, the disclosures of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates in general to the field of oxidativecatalysis, and more particularly, to the use of a dibenzothiophene (DBT)model reaction system to investigate the oxidation properties of silicagel (SiO₂).

BACKGROUND

Without limiting the scope of the invention, its background is describedin connection with the oxidative properties of silica gel and relatedcompounds.

Developed countries are setting new standards for the allowable amountof sulfur in diesel. By 2009 the allowable amount of sulfur will be15/10 ppm in diesel fuel₁. Currently, hydrodesulfurization processes areutilized to remove sulfur from fuels. These processes involve hightemperatures from 350° C.-700° C. and high pressures of about 3-5 MPa ofH₂ ² depending on the quality of the oil.

U.S. Pat. No. 7,713,408 issued to Breivik and Knudsen (2010) teaches aprocess for the catalytic hydrotreating of a hydrocarbon feed stockcontaining silicon compounds comprising the steps of contacting the feedstock in presence of hydrogen with a first hydrotreating catalyst beingarranged in at least two reactors being connected in series at an outlettemperature of up to 410° C. to reduce content of the silicon compoundsin the feed stock; cooling of the feed stock such treated to atemperature of between 280° C. and 350° C.; and contacting the cooledfeed stock with a second hydrotreating catalyst at conditions beingeffective in reduction of sulfur compound and nitrogen compoundconcentration.

From the economic and environmental point of view, it would be moresuitable if low-temperature and low-pressure systems could be developedto remove sulfur from fuels. Higher temperature and pressure processesdecrease the catalyst life and it involves higher H₂ consumption andthus, higher costs. In addition, high-temperature and high-pressureprocesses result in the generation of H₂S, a highly toxic compound.

Another reason why if is important to find another method to removesulfur is because sulfur compounds such as methyl ethyldibenzothiophene, 4-methyl dibenzothiophene, 3 methyl dibenzothiopheneand others are poorly reactive under the hydrodesulfurizationprocess³⁻⁵. In order to decrease the levels of sulfur in gasoline andmeet environmental regulations it is necessary to eliminate these sulfurcompounds from crude oils.

There are other promising techniques for the removal of sulfur, such asbio-desulphurization, extraction, selective adsorption, extraction withionic liquids, phase transfer catalysts, and oxidative desulfurizationto remove sulfur compounds⁶⁻⁸. Most of these techniques utilizeoxidizing agents such as NO₂, H₂O₂ and ter-butyl-hydroperoxide⁹⁻¹⁰. Oneadvantage of using these techniques is that sulfur can be removed atrelatively low temperatures and atmospheric pressure. However, thecatalysts utilized in the aforementioned techniques, are made ofruthenium and other expensive metals. In addition, the constant use ofstrong oxidizing agents such as hydrogen peroxide can also becomeexpensive.

U.S. Pat. No. 4,329,221 issued to Farcasiu et at. (1982) provides aprocess for reducing the metal, sulfur, and nitrogen content ofpetroleum residual oils. The process involves contacting a mixture ofhydrocarbon feedstock and hydrogen-donor solvent with a catalystcomposition comprising a naturally occurring porous metal ore such asmanganese nodules.

in addition to the high temperature and high pressure catalystscurrently available, there are other techniques for the removal ofsulfur, such as, selective adsorption, extraction with ionic liquids,phase transfer catalysts, and oxidative desulfurization to remove thesesulfur compounds⁶⁻⁸. For example, Mo/Al₂O₃ catalysts have been used inthe oxidative desulfurization (OD) process using hydrogen peroxide asthe oxidizing reagent, it has also been proposed to use Ti₃(PW₁₂O₄₀)₄catalyst, which also requires the use H₂O₂ ⁹⁻¹⁰. There has been researchin oxidative desulfurization using decalin solution with sulfurcompounds of dibenzothiophene (DBT), where Bu hydroperoxide (TBHP) wasused as the oxidant and molybdenum oxide catalyst supported on resinswas used as catalyst¹¹. Superoxides for instance, potassium superoxide,has been demonstrated as an alternative oxidant for the oxidativedesulfurization process¹². For model compounds of benzothiophene,dibenzothiophene, and a number of selected diesel oil samples, sulfurremoval greater than 90% and as high as 99% has been accomplished usingpotassium superoxide¹².

U.S. Patent Publication No. 20100038287 (Menegassi et al., 2010) relatesto a process for removing organic silicon compounds from hydrocarbonstreams by contact with an adsorbent and hydrogen. The adsorbent iscomposed of lamellar double hydroxides and group VI-B or group VIIIhydrogenating metal. More specifically, the process of the presentInvention involves a stage of activation for formation of the lamellardouble hydroxide, and maintaining the phase of lamellar double hydroxideby adding water.

Peroxides have been used to oxidize DBT as have oxidizing solvents suchas aldehydes and carboxylic acid³⁵⁻³⁶. For example, it has been reportedthe use of a surfactant-type decatungstates for the oxidation of DBT.This reaction requires hydrogen peroxide²⁴. Also, oxidativedesulfurization of dibenzothiophene catalyzed by Keggin-type H₃PMo₁₂O₄₀and Na₃PMo₁₂O₄ using hydrogen peroxide as the oxidizing agent is foundin the literature²⁵.

SUMMARY

The present invention overcomes these and other problems in the priorart, and; describes novel compositions and methods for making and usingacidic silica (pH 0-4) to oxidize dibenzothiophene (DBT) todibenzothiophene sulfone under reflux conditions between 50° C. and 210°C. in the presence of a hydrogen donor solvent. In addition, thecombination of silica with gold speeds up the oxidation process. Thecatalysts were characterized using x-ray diffraction (XRD), infraredspectroscopy and x-ray fluorescence (XRF). Infrared spectroscopy wasalso used to follow the oxidation of DBT to DBT sulfone.

In one embodiment the present invention is a method of treating asulfur-containing hydrocarbon heavy feed. The method of the presentinvention first comprises the step of mixing the sulfur-containinghydrocarbon heavy feed with a hydrogen donor solvent and an acidifiedsilica to form a mixture followed by oxidizing the sulfur in the mixturewith an oxidant at a temperature between 50° C. and 210° C., wherein theoxidation lowers the amount of sulfur in the sulfur-containinghydrocarbon heavy feed by at least 90%. The heavy feeds as described inthe present invention comprise asphaltene, tar sands, bitumens, heavypetroleum or mixtures thereof. In one aspect, the hydrogen donor solventis selected from a group comprising hydrogen, natural petroleum, bases,alcohols, decahydronaphthalene, and tetrahydronaphthalene. The oxidantis air or a mixture of air and O₂. In another aspect, the acidifiedsilica has a pH in the range from 0 to 2. In yet another aspect thesilica comprises an amorphous silica and/or a silica gel. In one aspect,the temperature for oxidizing the mixture is 120° C. to 160° C. Inanother aspect the temperature for oxidizing the mixture is 120° C.,125° C., 130° C., 135° C., 140° C., 145° C., 150° C., 155° C., and 160°C. In another aspect, the method of the present invention furthercomprises the step of adding a reduced noble metal catalyst or a mixtureof a noble metal and one or more acidic catalysts, wherein the acidiccatalysts comprise zeolites, silica, alumina or combinations thereof.The noble metal catalyst, comprises reduced gold, platinum, silver,palladium, or mixtures thereof. Another aspect of the present inventionis directed towards the solvents comprising at least one of decalin,tetralin, toluene, heptane, and dodecane. In another aspect, the finalsulfur concentration in the hydrocarbon heavy feed has less than 1,000,500, 250, 200, 100, 50 or 10 ppm sulfur after treatment. Yet anotheraspect describes a treated hydrocarbon feed made by the method of thepresent invention.

In another embodiment, the present invention describes a method oftreating a sulfur-containing hydrocarbon heavy feed comprising the stepsof: mixing the sulfur-containing hydrocarbon heavy feed with a hydrogendonor solvent and an amorphous acidified silica to form a mixturewherein the hydrocarbon heavy feed comprises asphaltene, tar sands,bitumens, heavy petroleum or mixtures thereof, and oxidizing the sulfurin the mixture at a temperature between 120° C. and 210° C., wherein theoxidation lowers the amount sulfur in the sulfur-containing hydrocarbonheavy feed to less than 1,000 ppm sulfur. In one aspect, the hydrogendonor solvent is selected from a group comprising hydrogen, naturalpetroleum, bases, alcohols, decahydronaphthalene, andtetrahydronaphthalene. In one aspect, the acidified silica ahs a pH inthe range from 0 to 2. In yet another aspect, the silica comprises asilica gel.

In another aspect of the present invention, the temperature foroxidizing the mixture is 120° C. to 160° C., and then oxidation iscarried out in air or a mixture of air and O₂. Another aspect of thepresent invention further comprises adding a reduced noble metalcatalyst or a mixture of a noble metal and one or more acidic catalysts,wherein the acidic catalysts comprise zeolites, silica, alumina orcombinations thereof. In yet another aspect reduced gold, platinum,sliver, palladium or mixtures thereof. In certain aspects, the silicacomprises reduced gold, platinum, silver, palladium or mixtures thereof.One aspect of the present invention is directed towards the solventscomprising at least one of decalin, tetralin, toluene, heptane, anddodecane. In a specific aspect, the heavy feed comprises asphaltene.

In yet another embodiment the present invention is method of treating asulfur-containing hydrocarbon heavy feed comprising asphaltenes, tarsands, bitumens, heavy petroleum or mixtures thereof, comprising thesteps of: mixing the sulfur-containing hydrocarbon heavy feed comprisingasphaltenes with a natural petroleum solvent and an acidified silica toform a mixture; oxidizing the sulfur in the mixture in air or in amixture of air and O₂ at a temperature between 120° C. and 210° C.,wherein the oxidation lowers the amount sulfur in the sulfur-containinghydrocarbon heavy feed to less than 100 ppm sulfur; and recovering theacidified silica.

Yet another embodiment is a method of treating a sulfur-containinghydrocarbon heavy feed comprising the steps of; mixing thesulfur-containing hydrocarbon heavy feed with a hydrogen donor solventand an acidified silica to form a mixture; oxidizing the sulfur in themixture at a temperature between 50° C. and 210° C., wherein theoxidation lowers the amount sulfur in the sulfur-containing hydrocarbonheavy feed by at least 90%; and recovering the acidified silica by waferextraction and/or a heavy feed treated by the above method. In oneaspect, the sulfur-containing hydrocarbon heavy feed comprisesasphaltenes, tar sands, bitumens, heavy petroleum or mixtures thereof.

In one embodiment, the present invention describes a method ofextracting sulfur from an oxidized hydrocarbon feed comprising the stepsof: (i) mixing a solution comprising a sulfur containing oxidizedhydrocarbon feed, an acidified silica, a hydrogen donor solvent, anyunreacted materials and reaction by-products with one or more polarorganic solvents, (ii) allowing the sulfur containing oxidizedhydrocarbon feed to migrate to the polar organic solvent phase, and(iii) removing the one or more polar organic solvents by evaporation torecover the sulfur. The hydrocarbon heavy feed of the present inventioncomprises asphaltenes, tar sands, bitumens, heavy petroleum or mixturesthereof. In one aspect the hydrogen donor solvent is selected from agroup comprising hydrogen, natural petroleum, bases, alcohols,decahydronaphthalene, and tetrahydronaphthalene. In another aspect theacidified silica has a pH range from 0 to 2 and further comprises anamorphous silica or a silica gel. In yet another aspect, the polarorganic solvent is selected from ethanol, methanol, n-propanol,isopropanol, n-butanol formic acid, acetic acid, 1,4-dioxane, THF,dichloromethane, acetone, acetonitrile, DMF, DMSO, or any combinationsthereof. In a further aspect, the present invention describes a sulfurextracted from a hydrocarbon feed by the method of the presentinvention.

Another embodiment, of the present invention is directed towards amethod of reducing asphaltene content in a crude oil comprising thesteps of: mixing the crude oil with an organic solvent and one or moresilica-noble metal nanoparticles to form a mixture, refluxing themixture to obtain a solid residue comprising asphaltenes, and filteringthe refluxed mixture to recover the asphaltene in the solid residue andthe final crude oil with reduced asphaltene content in the filtrate. Inone aspect the noble metals comprise gold, platinum, silver, andpalladium: or mixtures thereof. In another aspect the final crude oilhas less than 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, and 3% of asphalteneafter treatment. Yet another aspect describes a treated crude oil withreduced asphaltene content made by the method of the present invention.

in yet another embodiment the present invention provides a method formid-distillate upgradation and for sulfur removal in a fuel comprisingthe steps of: (i) mixing the fuel with a hydrogen donor solvent and anacidified silica to form a mixture and (ii) oxidizing the sulfur in themixture in air or a mixture of air and O₂ at a temperature between 50°C. and 210° C. The fuels that are treated by the method of the presentinvention comprise diesel, heavy petroleum, asphaltene, tar sands,bitumens, or mixtures thereof. In one aspect, of the method of thepresent invention the hydrogen donor solvent is selected from the groupconsisting of hydrogen, natural petroleum, bases, alcohols,decahydronaphthalene, and tetrahydronaphthalene. In another aspect, theacidified silica has a pH range from 0 to 2 and further comprises anamorphous silica or a silica gel. The temperature for oxidizing themixture as described in another aspect of the method of the presentinvention 120° C. to 160° C. In yet another aspect, the method of thepresent invention further comprises the step of adding a reduced noblemetal catalyst or a mixture of a noble metal and one or more acidiccatalysts, wherein the acidic catalysts comprise zeolites, silica,alumina or combinations thereof.

in one aspect the method comprises adding reduced gold, platinum,silver, and palladium metal nanoparticles or mixtures thereof. Inanother aspect the silica comprises reduced gold, platinum, silver, andpalladium particles or mixtures thereof. In yet another aspect thesolvents comprise at least one of decalin, tetralin, toluene, heptane,and dodecane. In a specific aspect the method lowers the amount sulfurin the fuel by at least 90%. The fuel after the treatment: by the methodof the present invention has less than 1,000, 500, 250, 200, 100, 50 or10 ppm sulfur. Finally, the present invention describes a fuel madeaccording to the method provided by the present invention.

BRIEF DESCRIPTION OF THE FIGURES

For a more complete understanding of the features and advantages of thepresent invention, reference is now made te the detailed description: ofthe invention along with the accompanying figures and in which:

FIG. 1 shows the mid-IR of DBT after reaction with silica grade 22 andlab synthesized silica: (FIG. 1A) DBT after silica grade 22 run at 160°C. (FIG. 1B) DBT after lab synthesized silica at pH 0-2, (FIG. 1C) DBTsulfone standard, (FIG. 1D) DBT standard;

FIG. 2 shows the far IR of DBT after reaction with; (FIG, 2A) Silica gelgrade 22 at 180° C., (FIG. 2B) DBT after reaction with lab synthesizedsilica at pH 1, (FIG. 2C) DBT sulfone standard, (FIG. 2D) DBT standard.This graph shows the optimum temperature to oxidize DBT to DBT sulfoneusing silica grade 22 occurs at 160° C. in decalin. All the absorptionbands are in the right place in the sample when compared to thestandard. The peak on DBT at 744 cm⁻¹ has shifted in the sample to alignup with the peak at 755 cm⁻¹ in DBT sulfone standard;

FIG. 3 shows the DBT after reaction with lab synthesized silica. Thedifferent spectra correspond to the silica dried at differenttemperatures: (FIG. 3A) DBT after silica lab synthesized dried at 380°C., (FIG. 3B) DBT after silica lab synthesized dried at 140° C. (FIG.3C) DBT after silica lab synthesized dried at 100° C., (FIG. 3D) DBTsulfone standard, (FIG. 3E) DBT standard;

FIG. 4 shows the far-IR of DBT after reacted with lab synthesized silicaand dried at different temperatures: (FIG. 4A) DBT after silica labsynthesized dried at 380° C., (FIG. 4B) DBT after silica lab synthesizeddried at 140° C., (FIG. 4C) DBT after silica lab synthesized dried at100° C. (FIG. 4D) DBT sulfone standard, (FIG. 4E) DBT standard;

FIG. 5A is a graph that shows different drying temperatures of thein-house lab synthesized silica in function of % of DBT removed;

FIG. 5B is a graph showing the effect of reaction temperature on theremoval of DBT in the presence of SiO₂ grade 22 and synthesized acidicSiO₂ calcinated at 380° C.;

FIG. 5C is a graph showing the comparison of time of the removal of DBTusing SiO₂ grade 22 and synthesized acidic SiO₂ (calcinated at 380° C.)at a reaction temperature of 160° C.;

FIG. 6 is a graph that shows the % of DBT removed in function of time.The % of DBT removed is shown in white when AuSiO₂ is used and when onlySiO₂ the % of DBT removed is shown in red;

FIG. 7 is a x-ray diffraction pattern of: (FIG. 7A) silica grade 22 and(FIG. 7B) lab synthesized silica;

FIG. 8 shows the x-ray diffraction pattern and the peak indexing ofDBT-sulfone standard (dotted line) and DBT after reaction with silicagel grade 22 (solid line); and

FIG. 9 shows oxidation of DBT to DBT-sulfone using AuSiO₂, a hydrogendonor solvent at a temperature of 160° C.

DETAILED DESCRIPTION

While the making and using of various embodiments of the presentinvention are discussed in detail below, it should be appreciated that,the present invention provides many applicable inventive concepts thatcan be embodied in a wide variety of specific contexts. The specificembodiments discussed herein are merely illustrative of specific ways tomake and use the invention and do not delimit the scope of theinvention.

To facilitate the understanding of this invention, a number of terms aredefined below. Terms defined herein have meanings as commonly understoodby a person of ordinary skill in the areas relevant to the presentinvention. Terms such as “a”, “an” and “the” are not intended to referto only a singular entity, but include the general class of which aspecific example may be used for illustration. The terminology herein isused to describe specific embodiments of the invention, but their usagedoes not delimit the invention, except as outlined in the claims.

As used herein the term “hydrogen donor solvent” includes any organic orinorganic medium which is capable of transferring hydrogen to thehydrocarbon feedstock component under the present invention processingconditions.

The term “silica” as used herein embraces all finely divided,precipitated silicas which are produced by a wet process and, inaddition, includes also pyrogenically obtained silicon dioxide. The term“silica gel” refers specifically to amorphous, regular density silicagel having a high surface area. More typically if is a coherent, rigid,continuous three-dimensional matrix or structure of generally sphericalparticles of silica having a pore volume of between about 0.5 and 3.5cc/g and an average pore diameter of between about 80 and about 600Angstroms. The term “amorphous silica” as used herein, refers toprecipitated silica, or silica prepared by flame hydrolysis, which canalso contain up to 20% aluminum oxide by weight. The filler contentamounts to from 30 to 80% by weight. The term “ppm” is used to denoteparts per million on an actives basis.

As used herein, the term “noble metals” Includes ruthenium, rhodium,palladium, osmium, iridium, gold and platinum. The term “acid catalysts”includes, in the broad sense, homogeneous mineral and organic catalysis,such as hydrochloric acid, sulphuric acid, acetic acid orpara-toluenesulphonic acid, but also, and preferably, heterogeneoussolid catalysts such as silica, alumina, silica-aluminas, zirconias,zeolites and acidic resins. The term “zeolite” as used herein refers toany porous natural or synthetic ceramic crystalline material that has asubstantially uniform pore structure. The diameter of the pores of azeolite generally range from about 2.5 to about 12 Angstroms. However,zeolites with a pore size of up to fen nanometers have been reported,(Science, Vol. 26, Mar. 25, 1994, pg. 1699). Most zeolites are metaloxides. The pore size of most zeolites is defined by the number ofmetal/oxygen atoms forming a ring or rings in the zeolite crystalstructure.

The term “crude oil feed” as used herein relates to any full range crudeoil from primary, secondary or tertiary recovery from conventional oroffshore oil fields and feedstock's derived there from. “Crude oilfeeds” may include any full range “syncrude” such as those can bederived from coal, shale oil, tar sands and bitumens. The crude may bevirgin (straight run) or generated synthetically by blending. The term“asphaltene” as used herein refers to a material obtainable from crudeoil and having an initial boiling point above 1200° F. (650° C.).

The present inventors recognized that silica-titania catalysts can beused for the mild oxidation of sulfur compounds, however, the reactionrequired the presence of hydrogen peroxide. Catalytic activity of TiO₂has also been tested and reported that it will oxidize DBT in thepresence of H₂O₂ ²⁶⁻²⁷. Furthermore, it has been reported that hydrogencan be oxidized to hydrogen peroxide using Au/SiO2 catalyst³⁴. Thepresence of a hydrogen donor solvent is important, and it was alsodiscussed how at a boiling temperature oxidation does not occur. Thisreaction may need the presence of both hydrogen and oxygen (whichescapes at boiling temperatures) to produce in situ H₂O₂.

The present invention describes the use of acidic silica (pH 0-4) tooxidize dibenzothiophene (DBT) to dibenzothiophene sulfone in refluxconditions between 50° C. and 210° C. In the presence of a hydrogendonor solvent. In addition, the combination of silica with gold speedsup the oxidation process.

Oxidative desulfurization techniques generally use oxidizing agents suchas NO₂, H₂O₂, and ter-butyl-hydroperoxide⁹⁻¹². The advantage of usingthese techniques is that sulfur can be removed at relatively lowtemperatures and atmospheric pressure. The major drawback is that all ofthem require the use of an oxidizing agent. The constant use of strongoxidizing agents such as hydrogen peroxide can also become expensive andit makes these catalysts inadequate to be used in a large scale.Biodesulfurization mechanisms have also been tried since some bacteriaare able to oxidize DBT at relatively low temperature and no pressure.In some cases, they bad starved organisms which need sulfur to survive,and then put them in a media were the only source of sulfur is DBT.Studies have shown that organisms would take sulfur out of DBT leavingbehind the carbon rings. Some examples Pseudomonas putida CECT5277,genetically modified organism, which biodesifurates DBT¹³. Another typeof bacteria are G. alkanivorans strain 1B was able to remove selectivelythe sulfur from DBT while keeping intact the remaining carbon-carbonstructure¹⁴. Bacteria successfully oxidize dibenzothiophene (DBT) todibenzothiophene-sulfone (DBT-sulfone) at low temperature, atmosphericpressure and without using an oxidizing agent; however, in order forthese bacteria to survive, they need specific conditions such asspecific pH and temperature which make them also inadequate technologyto be taken a large scale in a refinery.

Bulk gold is well known as a chemically inert element to oxidation. Itschemical properties of gold have been attributed to the relativisticstabilization of the 6s level. Gold's chemistry is determined by theeasy activation of the 5d electrons. It is also determined, as we knowthe electronic configuration of gold being [Xe] 4f¹⁴ 5d¹⁰ 6s¹, by itsdesire to acquire a further electron to complete the 6s² level and notto lose the one it has. However, chemical properties of bulk gold changein gold nanoparticles; recent studies have shown gold nanoparticles arecatalytically active in the oxidation of CO¹⁵.

in the present study, the oxidative catalytic properties of AuSiO₂ wereinvestigated. Two types of support (SiO₂) were utilized. One was silicagrade 22 commercially available and the other type was in-house labsynthesized silica. Silica gel was synthesized at different pH andtested in the model reaction. Infrared spectroscopy was used to followthe oxidation of DBT (dibenzothiophene) to DBT-sulfone using thein-house lab synthesized silica at the different pH. The oxidationreactions were also monitored at different reaction temperatures. X-raydiffraction was used to characterize the catalysts before and after thereactions. In addition, x-ray diffraction showed the conversion of DSTto DBT sulfone. HPLC (High performance liquid chromatography) techniquewas used to determine the percentage removal of DBT.

Silica gel grade 22: Silica gel grade 22 was obtained from Alfa Aesarcompany (Ward Hill, Mass., USA). Oxidation properties of silica gel weretested using the model reaction. A solution using DBT anddecahydronaphtalene (decalin) with a starting concentration of 2000 ppmof sulfur was prepared. Silica gel grade 22 was added to the solution,and the conversion of DBT to DBT-sulfone was tested at six differenttemperatures. The temperatures tested were 50° C., 100° C., 120° C.,140° C., 180° C. and boiling temperature (190° C. to 210° C.). Differenttemperatures were tested to determine the optimum temperature at whichoxidation would occur. The duration of each reaction was 4 h. In orderto determine if the oxidation reaction depended only on the temperature,solvent or both, different types of solvents were used hydrogen andnon-hydrogen donor with different boiling temperatures. The usedsolvents were decahydronaphtalene (decalin), tetrahydronaphtalene(tetralin), heptane, dodecane, and toluene as solvents.

Synthesis of silica gel at different pH: Silica gel was prepared withslight modifications as previously reported¹⁵. Sodium metasilicate(Na₂SiO₃) and hydrochloric acid (HCl) were obtained from Alfa Aesar.Na₂SiO₃ was dissolved in water which gave a basic solution (pH 12-14).HCl was added to the solution under vigorously stirring to bring the pHdown to 10. The solution looked cloudy because precipitation started tooccur. The gel was then washed several times with water to remove anyNaCl and then washed with alcohol to remove any water. The gel was thendried at three different temperatures 100° C. (24 h); 140° C. (24 h) and380° C. (24 h). The same procedure was followed to synthesize SiO₂ at pH9 and 8. As the pH was getting closer to neutral, more precipitation wasobserved. At pH 7 SiO₂ gel Instantly precipitated out and the sameprocedure as previously described was followed. To synthesize SiO₂ gelat pH 6, 5, and 4, two different methods were used. One method consistedin doing the titration with HCl fast to avoid passing through the gelphase at pH 7. The other method consisted in bringing the pH down toabout 2, after that it was brought up with sodium hydroxide (NaOH) to pH6, 5, and 4.

Finally, SiO₂ was synthesized at acidic pH, HCl was added to thesolution of Na₂SiO₃ in water under vigorously stirring and very fast toreach a pH of 0. The solution went from clear to yellow. Then, thesolution was heated at a 100° C. to obtain a gel. The gel was washedwith water and alcohol and dried at the three different temperatures.The oxidative properties of SiO₂ synthesized at different pH were testedusing the model reaction. DBT (0.5 g) was dissolved in decalin (50 ml),0.5 g of SiO₂ was added and let the reaction stir for 4 h. The reactionswere tested at 6 different temperatures: 50° C., 100° C., 120° C., 140°C., 180° C. and boiling temperature of the solvent. Differenttemperatures were tested to determine the optimum temperature for theoxidation reaction to occur. Also, different solvents were tested:decalin, tetralin, toluene, heptane, and dodecane solvents were testedin the reaction. The use of different solvents was use to determine ifthe solvent or the temperature or both were important factors in theoxidation reaction of DBT to DBT-sulfone.

Synthesis of gold nanoparticles on silica: Silica was dispersed inwater. A 3 mM solution of gold was prepared by dissolving HAuCl₄ (soldtetrachloroaurate) in water. The gold solution was then added to thedispersed silica. Reduction of gold on the silica was accomplished usingNaBH₄. Gold was reduced from Au³⁺ to Au⁰. The nanoparticles were thenwashed several times with distilled wafer and centrifuged to wash outsalts from the precursors. Then, they were oven dried at: a temperatureof 100° C.

X-ray diffraction analysis (XRD): The x-ray diffraction data wascollected using a D5000 X-ray diffractometer with Cu-Kα radiation whichits wavelength corresponds to 1.540562. The start angle was 5 degreesand the stop angle was 45 degrees. This range is where DBT and DBTsulfone diffract that is why it was chosen. The electron flux was 10kEv. The slits used where 0.1 and 1.0, X-ray analyses were performed onthe silica before running the reaction. X-ray diffraction was used tocharacterize the size of the gold nanoparticles before and after thereaction with DBT. After the reaction, the solutions of DBT, solvent,catalyst and conversion products were left to evaporate. After thesolvent is gone, all the silica concentrates on the bottom of the bigwatch glass. If was then easy to remove the silica. Then the solid leftbehind was mixed in a homogenous mixture and a representative sample wastaken and analyzed using x-ray diffraction.

X-ray diffraction was also performed on the silica, removed toinvestigate any changes occurred in the silica structure. In addition,after the mixture of DBT and DBTsulfone obtained was analyzed,unconverted DBT was extracted using decalin a non-polar solvent tocalculate the mass balance ratio of DBT to DBT-sulfone. DBT sulfone iscompletely insoluble in decalin and the other non-polar solvents used inthe different reactions. DBT-sulfone showed solubility in ethanol andacetone. However, acetone was not used to do the extractions because DBTis also soluble in acetone.

FT-IR Data collection: Infrared studies were carried out with a BrukerFTIR-IFS 66 v. The samples for IR measurements were prepared as pelletsby embedding the sample in a polycrystalline KBr matrix. The pressureapplied to make the pellets was 5 MPa. A background collection was runbefore each sample collection. After being treated with the catalysts,the solutions of the different solvents, DBT, and the catalyst were leftin the hood to slowly evaporate the solvent. The evaporation wasperformed in big watch glasses. After the solvent is gone, all thesilica concentrates on the bottom of the big watch glass. The silica wasthen removed. Then the solid left behind was mixed in a homogenousmixture and a representative sample was taken and analyzed usinginfrared spectroscopy. DBT and DBT sulfone standards were mixed indifferent percentages to compare them to the samples and determine thepercentage of DBT and DBT sulfone.

In addition, after the mixture of DBT and DBT-sulfone obtained wasanalyzed, DBT was extracted using decalin. DBT sulfone is completelyinsoluble in decalin and the other non-polar solvents used. After theextraction was performed, the mass balance was calculated and itconfirmed the data obtained from the infrared spectroscopy analysis.When the reactions were run in the temperature range of 100° C. to 140°C., it was not possible to separate completely DBT-sulfone from thesilica not even using a non-polar solvent.

High Performance Liquid Chromatography (HPLC): High Performance LiquidChromatography was used to determine the percentage of DBT removed. HighPerformance Liquid Chromatography (HPLC) was performed with a SPHERI-5(5 micron) Silica Based column, a Spectra-Physics Spectra System P1500gradient pump, UV2000 defector, and Winner for Windows Software. Themobile phase normally used was 95% hexanes, 5% isopropanol by volumewith helium solvent de-gassing. The flow rate was set to 1 mL/min. andthe detector was set to a 256 nm wavelength, all at room temperature. A1 μl aliquot of analyte was used, in some samples the injection amountwas higher to enhance the signal since it appeared, too weak. Acalibration curve was obtained by using four different concentrations ofDBT. The R factor of the calibration curve was 99%. Then using the lineequation y=mx, y corresponded to the counts, m to the slope of the curveand x was calculated to determine the concentration of DBT that wasremoved, in order to determine the role of gold on the silica, theconcentration of DBT was followed at three different times using justSiO₂ and AuSiO₂.

XRD Results: X-ray diffraction patterns of DBT after treated with theAuSiO₂ and DBT-sulfone standard are shown in FIG. 8. Cerius software wasused to assign the h k l planes, DBT-sulfone was modeled using the cellparameters and atomic positions as previously reported¹⁷. The unit cellparameters used were a=10.09 Å, b=13.89 Å, c=7.22 Å and β=93.5°. Thespace group used was C2/c. The x-ray diffraction patterns showed adifference in intensities (FIG. 8). Reflections at 13.30 and 22.14 2theta that correspond to the planes 020, and 220 are the same intensityin DBT-sulfone standard and DBT after treated with silica gel. However,reflections at 11.28, 16.86, 17.20, 18.32, 25.88, 27.51, and 38.322theta corresponding to 110, −111, 021, 040, 221, 041 and −113 planesare a lot higher than in the treated sample. Usually, intensify in x-raydiffraction is concentration related. Yet, the ratio of the intensitiesbetween the two reflections at 11.28 and 16.6 2 theta, which are themain peaks in DBT-sulfone standard, is 5.31. The ratio of theintensities in the treated sample between the peaks at 11.28 and 16.69 2theta is 0.78. In addition, the ratio of intensities of 11.24 to 16.88is 0.73 in the treated sample whereas in the DBT-sulfone standard is0.52. Since the ratio of the intensify of the peaks is different betweenDBT-sulfone standard and the sample treated, the difference in Intensityis not concentration dependent. The treated sample may have adoptedpreferred Orientation in the 110, −111, 021, 040, 221, 041 and −113planes since they are the predominant peaks. It is possible the heightpeaks are different just because the treated sample was more crystallinethan the purchased sulfone. The way the treated sample was extractedfrom the solvent was by slow evaporation which led to the formation ofDBT-sulfone crystals.

Only when the reaction was run at higher temperatures between 160° C.and 180° C., DBT-sulfone crystals could be extracted and observed in thex-ray diffraction Pattern. When the reaction was run at a lowertemperature between 50° C. and 140° C. DBT-sulfone could not becompletely isolated and the x-ray diffraction pattern showed silica andDBTsulfone peaks. Even though silica gel is amorphous it does have abroad peak at about 20° 2theta. In this region DBT-sulfone has manyreflections that could not be observed when the reactions were run atlower temperature.

Reactions using the in-house lab synthesized silica were also run atdifferent temperatures. However, the best percent removal of DBT, asoccurred in the case of silica gel grade 22, was obtained when thereactions were run at 160° C. In addition, silica gel grade 22 and theacidified silica synthesized and dried at 380° C. were characterizedusing also x-ray diffraction (FIG. 7A and FIG. 7B). X-ray diffraction ofin-house lab synthesized silica dried at 100° C. and 140° C. are notshown but the x-ray diffraction pattern doesn't differ from the onebelonging to the in-house lab synthesized silica dried at 380° C.. Afterreaction, both samples were analyzed again using x-ray diffraction. Theylooked still the same as before reaction, as amorphous silica (data notshown).

FT-IR Results: The results of the reaction using DBT as the modelcompound are shown in FIGS. 1A-1D. These results correspond to thereactions carried at 160° C. using silica grade 22 and the labsynthesized silica (pH 2-0) as catalysts (FIGS. 1A and 1B). This samplehad an Initial concentration of 2,000 ppm of sulfur. The solvent usedwas decalin, FIG. 1C and FIG. 1D show the infrared spectrumcorresponding to DBT-sulfone standard and DBT respectively. The maindifferences that were observed when the reaction is run at differenttemperatures are in the range of 1000 to 1500 cm⁻¹. The absorption bandscorresponding to DBT-sulfone start appearing when the reaction is ran at100° C. (data not shown). This absorption bands appear in the range from500 to 800 cm⁻¹ belonging to SO vibrations are present. However,DBT-sulfone vibrations between 1000 cm⁻¹ and 1500 cm⁻¹ are not visiblebecause they are being masked by the presence of the silica, whichabsorbs in the range of 1000 and 1500cm−1 (data not shown). As thereaction is run at higher temperatures, the absorption bands ofDBT-sulfone standard in the range of 1000 to 1500 cm⁻¹, start becomingvisible in the samples treated with the-catalyst. Based on this data, itis suggested that at lower temperatures, DBT is adsorbed onto the silicaand oxidized. As the temperature at which the reaction is run Increases(160° C.-180° C.), the silica releases the DBT already oxidized asDBT-sulfone back to the solution as shown in FIG. 1A all the vibrationspresent in the spectrum correspond to DBT-sulfone.

in FIGS. 2A-2D, the infrared spectrum is shown only from 800 to 400 cm⁻¹wavenumbers because it is where the C—S and S—O ring vibrations occur.It is important to emphasize the difference in the infrared spectrumafter the catalyst treatment at 160° C. (FIG. 2A). The shift in the peakat 744 cm⁻¹ occurs in the treated sample and the absorption bandscorresponding to S—O vibrations appear in the 600-500 cm⁻¹ range (FIG.2A). FIG. 2B shows the far IR of DBT after reaction with lab synthesizedsilica at pH 1.0. Comparing the treated sample to DBT standard (FIG. 2D)there is no visible DBT vibrations.

Comparing the treated sample to DBT sulfone standard (FIG. 2C), all thevibrations of the DBT sulfone standard are present in the treatedsample. Based on the aforementioned results, it was determined the rangetemperature, at which the oxidation of DBT to DBT-sulfone occurs, isbetween 100° C. end 180° C. in decalin. Yet, in order to obtain thesulfone detached from the silica, the reaction needs to be carried athigher temperature (160° C.-180° C.),

The main differences that were observed when the reaction is run atdifferent temperatures are in the range of 1000-1500 cm⁻¹. Theabsorption bands corresponding to DBT-sulfone start appearing when thereaction is run at 100° C. (data not shown). However, DBT-sulfonevibrations between 1000 cm⁻¹ and 1500 cm⁻¹ are masked by the presence ofthe silica, which absorbs in the range of 1000-1500 cm⁻¹ and thus notvisible in the FT-IR spectra. As the reaction temperature increased: theabsorption bands of DBT-sulfone standard in the range of 1000-1500 cm⁻¹,began to become visible in the samples treated with SiO₂. Based on thesedata, it is suggested that a lower temperature DBT is absorbed onto thesilica first and is subsequently oxidized. As the temperature at whichthe reaction is run increases (160° C.), the silica releases theoxidized DBT (DBT-sulfone) back to the solution. The reaction was alsocarried at boiling temperature of the decalin (190° C.). At boilingtemperature, oxidation did not occur, not even partial oxidation. Theanalyses at boiling temperature showed no decrease of concentration ofDBT, or the presence of DBTsulfone. Therefore, the temperature range atwhich reactions are carried is an important factor in the oxidation ofDBT.

FIGS. 3A-3E is showing the infrared spectra corresponding to DBT afterthe reaction with lab synthesized silica. The reaction was carried at160° C., FIGS. 3A-3C shows DBT after reaction with lab synthesizedsilica dried at different temperatures 100° C., 140° C. and 380° C.FIGS. 3A and 3B show DBT after reaction with lab synthesized silicadried at 140° C. and 380° C. respectively. FIG. 3C shows DBT afterreaction with lab synthesized silica dried at 100° C.. Absorption bandsof FIG. 3A and 3B coincide with the absorption bands in FIG. 3D(DBT-sulfone standard, FIG. 3E); however, when the lab synthesizedsilica is dried at 100° C., conversion of DBT to DBT sulfone is not asevident. FIGS. 4A-4E shows the far IR, FIG. 4A and 4B show all theabsorption bands corresponding to DBT sulfone. The shoulder at 734 cm⁻¹present in DBT-sulfone is broader in the treated samples with labsynthesized silica (FIGS. 4A and 4B). The broadening of the peak couldbe due to the presence of decalin (solvent where the reaction wascarried) which absorbs at this same wavenumber. FIG. 4C shows the far-IRof DST after reacted with lab synthesized silica dried at 100° C. FIGS.4D and 4E shows the far-IR of DBT sulfone and DBT standard,respectively.

HPLC Results: HPLC technique was used to confirm the percentageconversion of DBT to DBT-sulfone obtained from IR and mass balanceanalysis. The retention time for DBT was 4.2 minutes. The startingconcentration of DBT was 2,000 ppm of S. FIG. 5A shows the % of DBTremoved in function of the drying temperature of the lab synthesizedsilica. It can be observed that as the drying temperature increases, the% of DBT removed increases too. As it can be seen in FIG. 5A when thegel is dried at 100° C. only a 20% reduction of the DBT concentrationwas observed. The concentration of DBT removed when the SiO2 wascalcinated at 140° C. was 40%. However, at a calcination temperature of380° C. (above the critical point of water), a reduction of 80% of theDBT concentration was observed. Thus, the drying temperature that gaveout the best % of DBT removal was 380° C.. It is possible that thisresult was obtained because it has been reported that drying silica at380° C. (above the critical point of water) yields a material with highsurface area. The present inventors performed a comparison betweencommercially available silica and the in-house-synthesized silica forthe oxidation of DBT was performed. The reactions of both thein-house-synthesized silica and the commercial silica with DBT wereperformed at 100° C., 140° C., and 160° C. and are shown in FIG. 5B.From the three temperatures used 100° C., 140° C. and 160° C., thereaction run at 160° C. was the one that showed the largest removal ofDBT. Furthermore, as shown in Table 1, that the oxidation of DBT toDBT-sulfone occurs only in the presence of a hydrogen-donating solventsuch as decalin or tetralin. No oxidation was observed when non-hydrogendonor solvents such as heptane and toluene were used. The conversionusing either tetralin or decalin is approximately the same. Only datausing decalin as a solvent are shown in FIG. 5B. According to FIG. 5B,the highest removal, 85%, of DBT occurred at 160° C. FIG, 5C shows thetime requirements for the removal of DBT at 160° C., using samplingtimes of 60, 120, and 240 min. The reaction requires 240 min to reach80-85% removal of DBT.

TABLE 1 Results of reactions of DBT with different SiO₂: commerciallyavailable SiO₂ grade 22, SiO₂ basic, SiO₂ neutral, and SiO₂ acid inhouse synthesis, using different solvents, and reaction temperatures.Reaction temperature % DBT Catalyst (° C.) Solvent removal SiO₂ grade 22160 Decalin 80 SiO₂ grade 22 160 Tetralin 85 SiO₂ grade 22 100 Heptane 0SiO₂ grade 22 110 Toluene 0 SiO₂ grade 22 160 Dodecane 0 SiO₂ neutral pH160 Decalin 0 SiO₂ basic pH 160 Decalin 0 SiO₂ acidic pH 160 Decalin 80SiO₂ neutral pH 160 Tetralin 0 SiO₂ basic pH 160 Tetralin 0 SiO₂ acidicpH 160 Tetralin 84

FIG, 8 shows the % of DBT removed in function of time using SiO₂ andAuSiO₂. It can be observed that using gold nanoparticles increases the %of DBT removed at a given time. Table 2 shows a summary of the resultsof the reactions run using silica and the different solvents. As it wasshown previously, temperature influences the oxidation of DBT but alsothe reaction is solvent depended. Decalin is a well known hydrogen donormolecule which boils at 190° C.. The oxidation reaction was also carriedin tetralin (1,2,3,4 tetrahydronaphtalene) at the same temperatures thedecalin reaction was carried, 100° C., 120° C., 160° C., 195° C. andboiling temperature. The boiling temperature of tetralin is 205° C., Thereactions carried in tetralin had the same behavior the reactionscarried in decalin had. At lower temperatures, the DBT-sulfone was stuckon the silica and at higher temperatures was released back to thesolution. At the boiling temperature of tetralin and decalin, oxidationdidn't occur. As temperature increases, gas solubility decreases as ifis known from Henry's Law. It is possible at boiling temperature thesolvents degas and there is no more oxygen available to oxidize DBT.Non-hydrogen donor molecules were also used as solvents. The reactionswere carried in heptane, dodecane and toluene at different temperatures.Oxidation of DBT didn't occur in any of these solvents at anytemperature. It was concluded a hydrogen donor solvent was necessary tooxidize DBT.

TABLE 2 List of different reactions carried out and the percentconversion from DBT to DBT-sulfone. % conversion of Temperature Solventused DBT to DBT- Catalyst Reaction in reaction sulfone Silica lab 160°C. Decalin   0% synthesized neutral pH Silica lab 160° C. Decalin   0%synthesized at basic pH Silica lab 160° C. Decalin 80.4% synthesized atacidic pH (0-2) Silica lab 160° C. Tetralin   0% synthesized neutral pHSilica lab 160° C. Tetralin   0% synthesized at pH basic pH Silica lab160° C. Tetralin 85.3% synthesized at acidic pH (0-2) AuSiO₂ 160° C.Decalin 90.5% AuSiO₂ 160° C. Tetralin 92.4%

Table 1 shows a summary of the results of the reactions run using silicaand different solvents. As can be seen in Table 1, both the reactiontemperature and solvent directly affect the oxidation of DBT toDBT-sulfone. The oxidation reaction was also carried out in tetralin(1,2,3,4 tetrahydronaphthalene, data shown in Table 2) at the sametemperatures at which the decalin reaction was carried out, 100° C.,120° C., and 160° C., The reactions carried out in tetralin had the samebehavior as the reactions carried out in decalin. At lower temperatures,the DBT-sulfone was stuck on the silica and at higher temperatures wasreleased back to the solution. At the boiling temperature of tetralinand decalin, oxidation did not occur. This suggests that dissolved gases(such as O₂) in the solvent may be partially responsible for theoxidation; as the temperature Increases the solubility of the gasesdecreases. At the boiling point of the solvent ail the dissolved gasesare released and thus there is no gas left in the solution for theconversion of DBT to DBT-sulfone. In addition, the reactions were alsostudied in non-hydrogendonating solvents; heptane, dodecane, and tolueneat different temperatures. The oxidation of DBT to DBT-sulfone did notoccur in either of these solvents at any tested temperature. Thesefindings suggest that in addition to needing a dissolved gas in thesolvent a hydrogen-donating molecule is also necessary to oxidize DBT.

In addition to temperature and solvent, the pH at which silica gel wassynthesized had a role in the oxidation reaction. Silica gel synthesizedin the pH range of 3-10 did not oxidize DBT. Oxidation of DBT onlyoccurred when silica synthesized at pH in the range of 1-2 was used. Thestructure of the silica is depending upon what pH the silica gel issynthesized. An acidic pH silica gel will have H+ embedded in the matrixor OH− at a basic pH¹⁸. Under acidic conditions condensation occursmainly between neutral silanol groups (Si—OH) and protonated silanolgroups (Si—OH+) located at the monomers and at the ends of polymericchains leading to the formation of linear polymers¹⁹. In basicconditions, condensation occurs by attack of a deprotonated silanol(Si—O−) located at the middle of chains, to a neutral silanol (Si—OH) orSi—OR group which are at the ends of chains. The aggregation processesare different for pH=2 and for pH≧6¹⁹. In the former case there iscluster-cluster aggregation, and in the latter case there is reactionlimited monomer-cluster aggregation. In this way, for basic conditions,slioxane bonds are broken producing monomers that are not hydrolized.Comparatively, the acid-catalyzed or acidic SiO₂ compounds containhigher concentrations of adsorbed water, silanol groups, and unreactedalkoxy (depending on the source of the Si in the synthesis) groups thanbase-catalyzed precipitates¹⁸. From the results in the present inventionthe oxidation of DBT occurs only in the presence of acidic silica, whichsuggests that the SiOH+ groups are important in the reaction mechanism.For neutral conditions, the hydrolysis rate is low leading to thepresence of monomers that are partially or non-hydrolyzed at all²⁰⁻²¹.Thus, under neutral and basic conditions a large concentration ofmonomers remains. These monomers wilt condense preferentially withclusters as the condensation process occurs preferentially betweendeprotonated silanol species and neutral silanol species²⁰⁻²¹.Acid-catalyzed silica gels contain higher concentrations of adsorbedwater, silanol groups, and unreacted alkoxy groups than did thebase-catalyzed precipitates²².Therefore, the fact that oxidation of DBToccurs only when silica gel is synthesized at an acidic pH, it ishypothesized, H⁺ protons are necessary to drive the oxidation reaction.

It has been reported that sulfides can be oxidize to sulfoxides usingsupported HNO₃ on silica gel and polyvinylpyrrolidone (PVP) in thepresence of a catalytic amt of KBr or NaBr²³. Oxidation using silica gelmay be an acid catalyzed reaction since the silica has to be acidic andthe solvent a hydrogen donor²⁴⁻²⁵. Drying temperature of the silica gelsynthesized did have an impact in the oxidation reaction. Silica geldried at 160° C., had the best percentage conversion of DBT to DBTsulfone. It was also the one that according to the data obtained fromthe x-ray diffraction pattern, had a similar structure to silicagrade22. Drying temperatures usually lead to structural changes. Hightemperature drying usually yields a crystalline structure. Thetemperatures used to dry the synthesized silica were not high enough toyield a crystalline structure. If the drying temperature of silica hadbeen higher the structure of the silica would had been affected. Thisassumption is made on the fact that quartz, which is a crystalline phaseof silica, was tested in the oxidation reaction. No conversion of DBT toDBT sulfone was observed.

There are no DBT oxidation reactions reported in literature which wouldrequire the presence of a hydrogen donor solvent. The literature reportsthe use of peroxides when oxidizing DBT and the use of oxidizingsolvents such as aldehydes and carboxylic acid²⁶⁻²⁷. For example, it hasbeen reported the use of a surfactant-type decatungstates for theoxidation of DBT. This reaction requires hydrogen peroxide²⁸. Also,oxidative desulfurization of dibenzothiophene catalyzed by Keggin-typeH₃PMo₁₂O₄₀ and Na₃PMo₁₂O₄ using hydrogen peroxide as the oxidizing agentis found in the literature²⁹. It has been reported the use ofsilica-titania catalysts for the mild oxidation of sulfur compounds butthe presence of hydrogen peroxide is needed. Catalytic activity of TiO₂has also been tested and reported that it will oxidize DBT in thepresence of H₂O₂ ³⁰⁻³¹. As already mentioned, there is plenty ofevidence H₂O₂ will oxidize DBT to DBT sulfone³²⁻³³ therefore, it is alsohypothesized the in-situ production of H₂O₂ by silica. It has beenreported that hydrogen can be oxidized to hydrogen peroxide usingAu/SiO₂ catalyst³⁴. The presence of a hydrogen donor solvent isimportant, and at a boiling temperature oxidation does not occur. Thisreaction may need the presence of both hydrogen and oxygen (whichescapes at boiling temperatures) to produce in situ H₂O₂.

Amorphous acidified silica (synthesized at an acidic pH) gel willoxidize DBT to DBT sulfone in the presence of a hydrogen donor solventin the temperature range of 50° C. to 210° C. depending on the boilingpoint of the hydrogen donor solvent. The current study addresses the useof acidified silica gel for the oxidative desulfurization of DBT in thepresence of a hydrogen donor solvent, at relatively low temperature andatmospheric pressure, with no oxidizing agent present in the reaction(FIG. 9). DBT has been used as a model compound of the sulfur containingcompounds present in heavy feeds. This model has been successful inpredicting the behavior of catalysts in the real feeds. According to theresults obtained, sulfur compounds in heavy feeds, could be oxidized andremoved with a polar solvent such as ethanol. Following the resultsobtained from the model reaction it is concluded that using acidifiedsilica is an inexpensive and efficient way to upgrade heavy feeds.

Process to extract the DBT-sulfone: After the reactions were run, thesolution of decalin and products can be mixed with 50 mL of ethanol.Using a separating funnel, the two phases can were separated. TheDBT-sulfone migrated to the ethanol due to the change in polarity in themolecule. The addition of the two oxygen atoms to the DBT, made theDBT-sulfone completely insoluble in decalin. Once the two phases wereseparated, the solvents were removed using a roto-evaporator.

Asphaltene reduction: In addition, to testing the catalysts in theDBT-model reaction, the present inventors also tested them in real crudeoil. The crude oil used contained 10% wt asphaltene. By definition,asphaltene is any fraction of the crude oil insoluble in heptanesolvent. The control reaction was run by refluxing 18 g of the crude oilin 30 ml of heptane for 4 h at 98° C. The solution was then filtered toobtain 1.8 g of the solid filtrated which corresponded to 10% asphalteneof the crude oil. Two separate reactions were also run using silica-goldnanoparticles, and iron-gold nanoparticles in crude oil (18 g). Thesolvent used was heptanes, the reflux temperature was 98° C. and theduration of the reactions was 4 h. The solutions were then filtrated andthe solids corresponded to 0.7 g and 1.44 g for silica-gold andiron-gold nanoparticles respectively. Therefore, the gold nanoparticleson silica can be used to reduce the number of asphaltene in crude oilbecause the results show a decrease of 10% to 4%.

The present invention Includes the use of acidic silica (pH 0-4) tooxidize dibenzothiophene (DBT) to dibenzothiophene sulfone in refluxconditions between 50° C. and 210° C. In the presence of a hydrogendonor solvent. The catalysts were characterized using x-ray diffraction(XRD), infrared spectroscopy and x-ray fluorescence (XRF). Infraredspectroscopy was also used to follow the oxidation of DBT to DBTsulfone.

It is contemplated that any embodiment discussed in this specificationcan be implemented with respect to any method, kit, reagent, orcomposition of the invention, and vice versa. Furthermore, compositionsof the invention can be used to achieve methods of the invention.

It will be understood that particular embodiments described herein areshown by way of illustration and not as limitations of the invention.The principal features of this invention can be employed in variousembodiments without departing from the scope of the invention. Thoseskilled in the art will recognize, or be able to ascertain using no morethan routine experimentation, numerous equivalents to the specificprocedures described herein. Such equivalents are considered to bewithin the scope of this invention and are covered by the claims.

All publications and patent applications mentioned in the specificationare indicative of the level of skill of those skilled in the art towhich this invention pertains. All publications and patent applicationsare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andIndividually indicated to be incorporated by reference.

The use of the word “a” or “an” when used in conjunction with the term“comprising” in the claims and/or the specification may mean “one,” butit is also consistent with the meaning of “one or more,” “at least one,”and “one or more than one.” The use of the term “or” in the claims isused to mean “and/or” unless explicitly indicated to refer toalternatives only or the alternatives are mutually exclusive, althoughthe disclosure supports a definition that refers to only alternativesand “and/or.” Throughout this application, the term “about” is used toindicate that a value includes the inherent variation of error for thedevice, the method being employed to determine the value, or thevariation that exists among the study subjects.

As used in this specification and claim(s), the words “comprising” (andany form of comprising, such as “comprise” and “comprises”), “having”(and any form of having, such as “have” and “has”), “including” (and anyform of including, such as “includes” and “include”) or “containing”(and any form of containing, such as “contains” and “contain”) areinclusive or open-ended and do not exclude additional, unrecitedelements or method steps.

The term “or combinations thereof” as used herein refers to allpermutations and combinations of the listed items preceding the term.For example, “A, B, C, or combinations thereof” is intended to includeat least one of: A, B, C, AB, AC, BC, or ABC, and if order is importantin a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB.Continuing with this example, expressly Included are combinations thatcontain repeats of one or more item or term, such as BB, AAA, MB, BBC,AAABCCCC, CBBAAA, CABABB, and so forth. The skilled artisan willunderstand that typically there is no limit on the number of items orterms in any combination, unless otherwise apparent from the context.

All of the compositions and/or methods disclosed and claimed herein canbe made and executed without undue experimentation in light of thepresent disclosure. While the compositions and methods of this inventionhave been described in terms of preferred embodiments, it will beapparent to those of skill in the art that variations may be applied tothe compositions and/or methods and in the steps or in the sequence ofsteps of the method described herein without departing from the concept,spirit and scope of the invention. All such similar substitutes andmodifications apparent to those skilled in the art are deemed to bewithin the spirit, scope and concept of the invention as defined by theappended claims.

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What is claimed is:
 1. A method of extracting sulfur from an oxidizedhydrocarbon feed comprising the steps of: mixing a solution comprising asulfur containing oxidized hydrocarbon feed, an acidified silica, ahydrogen donor solvent, any unreacted materials and reaction by-productswith one or more polar organic solvents; allowing the sulfur containingoxidized hydrocarbon feed to migrate to the polar organic solvent phase;and removing the one or more polar organic solvents by evaporation torecover the sulfur.
 2. The method of claim 1, wherein the oxidizedhydrocarbon feed comprises asphaltenes, tar sands, bitumens, heavypetroleum or mixtures thereof.
 3. The method of claim 1, wherein thehydrogen donor solvent is selected from the group consisting ofhydrogen, natural petroleum, bases, alcohols, decahydronaphthalene, andtetrahydronaphthalene.
 4. The method of claim 1, wherein acidifiedsilica has a pH range from 0 to
 2. 5. The method of claim 1, wherein theacidified silica comprises an amorphous silica or a silica gel.
 6. Themethod of claim 1, wherein the polar organic solvent is selected fromthe group consisting of ethanol, methanol, n-propanol, isopropanol,n-butanol, formic acid, acetic acid, 1,4-dioxane, THF, dichloromethane,acetone, acetonitrile, DMF, DMSO, and any combinations thereof.
 7. Asulfur extracted from a hydrocarbon feed by the method of claim
 1. 8. Atreated crude oil with reduced asphaltene content made by the method ofclaim
 1. 9. A method for mid-distillate upgradatlon and sulfur removalin a fuel comprising the steps of: mixing the fuel with a hydrogen donorsolvent and an acidified silica to form a mixture; and oxidizing thesulfur in the mixture in air or a mixture of air and O₂ at a temperaturebetween 50° C. and 210° C.
 10. The method of claim 9, wherein the fuelcomprises diesel, heavy petroleum, asphaltene, tar sands, bitumens, ormixtures thereof.
 11. The method of claim 9, wherein the hydrogen donorsolvent is selected from the group consisting of hydrogen, naturalpetroleum, bases, alcohols, decahydronaphthalene, andtetrahydronaphthalene.
 12. The method of claim 9, wherein acidifiedsilica has a pH range from 0 to
 2. 13. The method of claim 9, whereinthe acidified silica comprises an amorphous silica or a silica gel. 14.The method of claim 9, wherein the temperature for oxidizing the mixtureis 120° C. to 160° C.
 15. The method of claim 9, further comprising thestep of adding a reduced noble metal catalyst or a mixture of a noblemetal and one or more acidic catalysts, wherein the acidic catalystscomprise zeolites, silica, alumina or combinations thereof.
 16. Themethod of claim 9, further comprising adding reduced gold, platinum,silver, and palladium metal nanoparticles or mixtures thereof.
 17. Themethod of claim 9, wherein the silica comprises reduced gold, platinum,silver, and palladium particles or mixtures thereof.
 18. The method ofclaim 9, wherein the solvents comprise at least one of decalin,tetralin, toluene, heptane, and dodecane.
 19. The method of claim 9,wherein the method lowers the amount sulfur in the fuel by at least 90%.20. The method of claim 9, wherein the fuel has less than 1,000, 500,250, 200, 100, 50 or 10 ppm sulfur after treatment.
 21. A fuel made bythe method of claim 9.